Work in the field of dendritic molecules dates back to the early fifties with the publication of a theoretical paper by Flory, J.Am. Chem. Soc., 74, 2719 (1952). Basically, a dendritic molecule is a highly branched polymer molecule.
The prior art reports various ways to prepare such dendritic molecules. For example, Vogtle and coworkers, Synthesis 155 (1978) described a “cascade” approach. This approach is not capable of producing a dendritic molecule having a molecular weight of greater than 790 Daltons. More recently, Newkome used a nucleophilic displacement reaction on a multi-functional core to produce, after two stages of reaction, a cascade molecule coined “arboral” with molecular weights of up to 1600 Daltons. See, for example, Aharoni et al, Macromolecules 15, 1093 (1982); J. Org. Chem. 50, 2004 (1985); Newkome et al. J. Chem. Soc. Chem. Commum., 752 (1986); and Newkome et al. J. Am. Chem. Soc. 108, 849 (1986).
The most extensive published studies of dendritic molecules are directed to “starburst” polymers. See, for example, U.S. Pat. Nos. 4,507,466; 4,558,120; 4,568,737; 4,587,329; 4,737,550; and 4,857,599. Such “starburst” polymers are made by a divergent approach building the molecule from the core towards its extremities.
More recently, two co-inventors of this invention obtained a patent, U.S. Pat. No. 5,041,516, describing a novel convergent approach to produce dendritic molecules. In this approach, the molecule is built from the outside towards the core. This approach enables the accurate placement of one or more functional groups in the outer surface of the dendritic polymer.
Once formed by whatever method, the dendritic polymers have many uses such as polymer crosslinking agents, drug delivery systems, optoelectronic; carriers for synthetic enzymes and genetic materials, etc. In U.S. Pat. No. 5,041,516, at columns 5 and 6, lines 60-13 uses for dendritic polymers which include the formation of macromolecules having identifiable shapes such as “barbells”, “knots”, etc. is disclosed. The disclosure is, however, very limited as to how to make such structures. For example, with respect to barbells, the only disclosure of how to produce such a shape is limited to a “barbell” shape produced from 2 dendritic molecules having surface functional groups at which point they are joined together by a connecting linkage. This procedure is disclosed at col. 6, lines 12-13, and Example VI. The only other specific disclosure relates to a “knot” structure formed by reacting a dendritic polymer having opposed COOH groups with a simple dialcohol or a polyester or polystyrene based dialcohol. This is disclosed at col. 6, lines 1-11, and in Example IX. No other specific shapes are disclosed and no other processes are disclosed to make the specifically disclosed macromolecule shapes.
Tomalia et al U.S. Pat. No. 4,694,064 also discloses certain shaped macromolecules. Specifically, rod-shaped dendrimers are disclosed as useful shaped macromolecules. Tomalia et al U.S. Pat. Nos. 4,857,599 and 4,871,779 disclose chemical modification of dendritic arms onto a preformed polymer.
Shaped macromolecules may have particular uses that simple dendritic polymers do not. Accordingly, it is one of the objects of the present invention to develop novel macromolecule shapes.
Another object is to develop novel processes for preparing known macromolecule shapes.